uses the particular effects of a drug to augment cell and tissue function in order to restore it to normal. In other cases, drugs, which are meant to be therapeutic, cause damage to another tissue or type of cell as a side effect. For example, barbiturates cause damage to liver cells as they are degraded into their metabolites, which cause free radical damage. High intracellular glucose levels result in elevated intracellular calcium ion levels. As we have seen in hypoxic injury, an influx in calcium damages mitochondria and ultimately leads to cell necrosis.
3. Physical Injury
is a leading cause of cell injury. Some cells are damaged as their structures such as the cell membranes and the cytoskeleton are mechanically torn apart by force. These cells are generally consumed by phagocytic white blood cells (WBC’s). Trauma in the form of pressure can cause local ischemia and may alter the membrane potential of certain cells. cause damage to cells by two mechanisms. Exposure to low temperatures causes vasoconstriction and may cause ischemia as well as reducing reaction rate and affecting the fluidity of membranes. Extreme low temperatures cause water in the cytosol to freeze and expand, rupturing the cell membrane and causing necrosis. High temperatures increase metabolic rate and cause acidosis due to a buildup of carbon dioxide in the blood. Low pH damages membranes and proteins. Exposure to extreme high temperatures causes dehydration and combustion, or burning, of the hydrocarbon chains associated with cell structures. Extreme can cause mechanical damage to cells in much the same manner mechanical pressure dose. Sudden changes in atmospheric pressure cause structures and fluids in the body to expand or compress, without giving the rigid structures in the body time to adjust. For example, the rapid expansion of a fluid can exceed the membrane integrity causing the cell to rupture. Atmospheric pressure also affects the relative partial pressures of gasses inside the body. At low atmospheric pressure, the partial pressure of oxygen in the environment is lower than the partial pressure of oxygen in venous blood. This prevents oxygen from diffusing from the lungs into the blood causing hypoxia. or radiant energy directly causes cell death at high intensities as it ionizes the cytoplasm and effectively disrupts all metabolic reactions. At lower intensities radiation disrupts the replication of genes and leads to mutations that may alter cell function. Sources of radiation include nuclear energy fromweapons or power plants, x-rays, and ultraviolet rays from the sun. energy generates heat and causes burn damage in the same way high temperature does. Electricity also disrupts the electromagnetic gradients formed by cells, causes the activation or inactivation of voltage-gated membrane channels, and affects the membrane potential of electrically conductive cells such as muscles and nerves.
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